1. Technical Field
The present invention relates to the field of tubing and filtration devices and more specifically towards gauges.
2. Background Art
Currently, various devices exist for measuring pressure within disposable tubing because it can be very beneficial to obtain and monitor relevant flow characteristics of fluids passing through the tubing. While methods for obtaining such information have existed for a long time, no reliable low cost systems have been developed for disposable use.
One prior art device for measuring pressure within tubing utilizes disposable pressure sensors with a luer lock fitting, as in U.S. Pat. No. 4,576,181. However, this device can only be used with low flow rates and small tubing sizes. Further, the device requires a computer or electronic interface for the pressure readout. In general, disposable pressure sensors that are provided pre-sterilized have limitations in that they cannot be calibrated before their use. This is a key drawback to use in the biopharmaceutical industry because calibration prior to the use of pressure gauges is required during Good Manufacturing Practices (GMP) production.
Another prior art device is a ¾ inch mini sanitary (stainless steel) gauge tee with hose barb adapters. Although this device can measure pressure within tubing, it is in constant contact with the stainless steel gauge. As a result, contamination of the gauge tee can occur. Furthermore, considerable hold-up volume results (5-50 mL).
Especially when operating in a sterile environment with biologics or pharmaceuticals, minimal hold-up volume is preferred. Hold-up is an amount of fluid in a system that remains stagnant, generally caused by a branch or tee in a line for a valve, gauge, or measuring line. If allowed to remain in place, such hold-up fluid can dilute the end product being produced on a line with a gauge.
Anderson Instrument Co., Inc. describes a zero dead-leg instrument fitting that can be installed on lines as small as ½ inch. The fitting is a tee and can be connected to a gauge or transmitter. The fitting is made of stainless steel, thus the liquid flow is still in contact to stainless steel. The fitting is intended for multiple uses.
U.S. Pat. No. 5,000,049 to Cooper, et al., discloses an apparatus for measuring fluid pressure in a tube of a catheter. The tube can include threads for receiving a gauge. The tube is made of a biocompatible, nonpyrogenic and sterilizable material. A sealing diaphragm is provided between the fluid path and the pressure-sensitive diaphragm, preferably made of polyethylene, polyurethane, polyvinylchloride, or the like. Thus, the diaphragm sends a read-out to a gauge pointer and there is no contact of the fluid with metal. However, such a device could not be used readily in a biopharmaceutical process, as the gauge must be calibrated before and after use. Meeting GMP processing standards is required for processing biopharmaceuticals, and calibrating a gauge after use will jeopardize the batch processed if the calibration fails.
U.S. Pat. No. 6,117,086 to Shulze discloses a physiological pressure transducer coupled to a catheter through a disposable dome containing a shaped, compliant isolation media, which is in intimate contact with the reusable transducer diaphragm. The disposable dome is in the shape of a tee. The isolation media preferably forms inside of all sharp corners around the outer diameter of the diaphragm where it contacts the disposable dome, thus providing an extremely smooth and essentially straight fluid path without the entrapment of bubbles. Again, this device requires a gauge that must be calibrated before and after use, and thus could not be used in biopharmaceutical processes.
U.S. Pat. No. 6,978,636 to Motush, et al., discloses a portable device for measuring refrigerant pressure, including a hose with a first end connected to an actuator on a pressurized container and a second end connectable to a service port of an automobile air conditioner. A T-connector with a check valve and pressure gauge is disposed in the hose. In the preferred embodiment, at least one barb of the T-connector is rotatable and is a separate piece from the body of the T-connector. This enables the T-connector to rotate with respect to the hose so that the pressure gauge will always be viewable by the user. The T-connector is preferably made of die-cast zinc, thus there is metal contact of the fluid. The device interfaces with a threaded pressure gauge and allows fluid to pass up into the body of the gauge. Such a device could not be used in biopharmaceutical processes because the fluid is in contact with the gauge itself, allowing for contamination.
Accordingly, there is a need for a device that can accurately measure pressure of liquids in disposable tubing during various processes. Additionally, there is a need for a disposable device that allows for biopharmaceutical processing and eliminates batch cross contamination or expensive cleaning validation. Further, there is a need for a device that can be sterilized and allows for aseptic pressure monitoring of a process. There is a need for a device that reduces the amount of hold-up volume. Finally, there is a need for a device that provides measurement without product contact to the environment or the stainless steel gauge diaphragm.